Recently, there has been increasing demand for high image quality and high color reproducibility, i.e., faithful reproduction of colors existing in nature, for recording and reproducing captured video signals, for example, representation of deep crimson, which is the color of rose petals, the vivid emerald green color of ocean waters, and the like in more natural looking images.
Currently, sRGB standard is the industry standard color space which is standard for computer displays. However, due to the demand for color reproducibility described above, for example, reproducing apparatuses capable of reproducing a color image using an extended sRGB standard (referred to herein as “extended sRGB standard”) that defines a wider color space than a color space defined in the sRGB standard have been proposed.
For example, Patent Document 1 describes a color liquid crystal display apparatus implementing an extended sRGB standard. This color liquid crystal display apparatus uses, as light sources of a backlight device, a primary white light source having three wavelength fluorescent lamp that emits light with three or more wavelengths, and an auxiliary light source including at least one or more of a red light emitting diode that emits red light with a peak wavelength λpr set to λpr=645 nm, a green light emitting diode that emits green light with a peak wavelength λpg set to λpg=555 nm, and a blue light emitting diodes that emits blue light with a peak wavelength λpb set to λpb =440 nm to implement a wider color space than the color space defined in the sRGB standard.
For example, in case of using a primary white light source 21 and, as an auxiliary light source 22, a green light emitting diode 22G having a peak wavelength λpg=555 nm, a blue light emitting diode 22B having a peak wavelength λpb=440 nm, and a red light emitting diode 22R having a peak wavelength λpr=645 nm, display light emitted from a color liquid crystal display panel is measured using a colorimeter, and chromaticity points are plotted in an xy chromaticity diagram. Then, a color reproduction range shown in FIG. 17a is obtained.
FIGS. 17b, 17c, and 17d are diagrams showing green (G), blue (B), and red (R) regions to an enlarged scale, respectively. Note that the xy chromaticity diagrams of FIGS. 17a, 17b, 17c, and 17d also show the color reproduction range of the Adobe RGB standard, the XYZ colorimetric system defined by the International Commission on Illumination (CIE), the color reproduction range of the sRGB standard, and the color reproduction range in the case of using only the primary white light source 21 as a light source.
Furthermore, for example, Patent Document 1 further describes that a color filter including a red filter having a peak wavelength Fpr of a transmission wavelength range, satisfying 685 nm≦Fpr≦690 nm, and having a transmittance of zero for a transmission wavelength range of a blue filter, a green filter having a peak wavelength Fpg of a transmission wavelength range, equal to 530 nm, and having a half-width Fhwg of the transmission wavelength range, satisfying 90 nm≦Fhwg≦100 nm, as a result of reducing the transmittance of the green color filter for the transmission wavelength range of the blue filter, and a blue filter having a peak wavelength Fpb of a transmission wavelength range, satisfying 440 nm≦Fpb≦460 nm, is provided to enable significant increase in the color reproduction range.
For example, in a case where the primary white light source 21 and the auxiliary light source 22 are used and a color filter 19A including a blue filter having a peak wavelength Fpb=440 nm, a green filter having a peak wavelength Fpg=530 nm, and a red filter having a peak wavelength Fpr=690 nm and having a half-width Fhwg=90 nm of the transmission wavelength range of green light is provided, display light emitted from a color liquid crystal display panel is measured using a colorimeter, and chromaticity points are plotted in an xy chromaticity diagram. Then, a color reproduction range shown in FIG. 18a is obtained.
FIGS. 18b, 18c, and 18d are diagrams showing green (G), blue (B), and red (R) regions to an enlarged scale, respectively. Note that the xy chromaticity diagrams of FIGS. 18a, 18b, 18c, and 18d also show the color reproduction range of the Adobe RGB standard, the XYZ colorimetric system defined by the International Commission on Illumination (CIE), the color reproduction range of the sRGB standard, and the color reproduction range in the case of using only the primary white light source 21 as a light source.
Meanwhile, a demand for recording a video signal in a wider color space than a sRGB color space has also increased for recording apparatuses. In existing cases where a recording apparatus and a reproducing apparatus are compatible with the sRGB standard, the reproducing apparatus can faithfully reproduce a color of a video signal recorded by the recording apparatus.
In a case where a recording apparatus records a video signal in a wider color space than a sRGB color space and a reproducing apparatus supports only an existing sRGB color space, however, the reproducing apparatus reproduces the video signal by merely clipping it in a color space thereof, which does not enable reproduction of an original color of the video signal.
Further, like Patent Document 1, also in a case where a color image can be reproduced using the extended sRGB standard, if a video signal recorded by a recording apparatus has also been recorded using the extended sRGB standard, a reproducing apparatus will not be able to faithfully reproduce the color of the video signal unless it is possible to determine whether the video signal complies with the sRGB standard or the extended sRGB standard.
Note that Patent Document 2 describes an image reproducing apparatus that reproduces an image on the basis of an image set in which image data and color space identification information indicating a color space related to the image data are associated with each other. This image reproducing apparatus performs image reproduction tailored to individual cases where a color space specified by the color space identification information is a standard color space and a specific color space.
That is, in case of reproducing image data for which the color space specified by the color space identification information is a standard color space (e.g., the sRGB color space), the image reproducing apparatus performs basic color space conversion on the image data to generate reproduction image data. In case of reproducing image data for which the color space specified by the color space identification information is a color space other than the standard color space (e.g., the Adobe RGB (trademark of Adobe Systems Incorporated) color space or the like), on the other hand, the image reproducing apparatus performs device-dependent color space (e.g., sRGB color space or the like) conversion on the image data to generate reproduction image data.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-119295    Patent Document 2: Japanese Unexamined Patent Application Publication (Domestic Republication of PCT International Publication) No. 2004/077837